Introgression and Habitat Segregation in a Pair of Ladybird Beetle Species in the Genus Propylea (Coccinellidae, Coccinellinae) in Northern Japan

Abstract

The ladybird beetles Propylea quatuordecimpunctata and P. japonica have largely overlapping distributions in northern Japan, and in the laboratory produce fertile hybrids. In this study, we surveyed the distribution and morphological differentiation of these species and the hybrids in natural populations, with a focus on western Hokkaido, northern Japan. Phenotypic analyses were conducted for 987 individuals collected at 90 localities. In addition, the nuclear internal transcribed spacer-II (ITS2) region (549 bp) and part of the mitochondrial cytochrome c oxidase subunit I (COI) gene (700 bp) were sequenced for 620 individuals from 53 localities. Analyses of both phenotypic and genotypic features discriminated two distinct entities assignable to P. quatuordecimpunctata and P. japonica. However, individuals with intermediate phenotypes and/or genotypes also occurred extensively, indicating natural hybridization. Putative P. quatuordecimpunctata individuals were collected across a wide range of altitudes (30-600 m), whereas those of P. japonica were found mostly lower than 300 m alt. In addition, P. quatuordecimpunctata was dominant in semi-open habitats shaded by canopy foliage, whereas P. japonica was frequent in more open habitats. The perceived altitudinal difference in the distributions may thus in part be a consequence of this different habitat preference, as open habitats are more common at lower altitudes in the study area.

Dissecting natural hybridisation in longhorned beetles through an integrative approach: Further proof of reticulate evolution in Dorcadionini (Cerambycidae, Lamiinae)

“…Thus, inferences of current or past introgressive hybridisation in areas of sympatric occurrence have been reported in species of Lucanidae (Cox et al., 2013; Kubota et al., 2011; Solano et al., 2016), Scarabaeidae (Wirta, 2009), Geotrupidae (Tóth et al., 2019), Chrysomelidae (Campbell et al., 2011; Kastally et al., 2019; Quinzin & Mardulyn, 2014), Carabidae (Kosuda et al., 2016) and Meloidae (Salvador de Jesús‐Bonilla et al., 2018). Natural hybrids have been identified in a wide hybrid zone in Chrysochus , Chrysomelidae (Monsen et al., 2007; Peterson et al., 2001, 2005) and Propylea , Coccinelidae (Suga et al., 2016), but without clear evidence of introgression, while in two species of Gonioctena (Chrysomelidae), nuclear introgression was detected by whole genome sequencing (Lukicheva & Mardulyn, 2021). In the genus Carabus , hybrids were identified between numerous species, even belonging to different subgenera (Deuve et al., 2012; Mossakowski, 2016) while mitochondrial introgression has been detected based on comparison with nuclear markers and/or morphological traits (Mossakowski, 2016; Su et al., 2006 and references therein).…”